The present invention relates generally to apparatus and methods for uncoupling driving and driven mechanisms during operation thereof, and more particularly provides high speed, reusable and easily resettable accessory disconnect apparatus, and associated methods, for very rapidly decoupling an engine from a driven accessory without imposing excessive stress on either the disconnect apparatus or the accessory.
A wide variety of disconnect devices have heretofore been employed to uncouple driving mechanism, such as engines, from accessory devices which they customarily operate by means of a drive shaft coupled at its opposite ends to the engine and accessory. However, especially in high speed applications, conventional disconnect devices present one or more of several well known and long-standing problems.
As an example, in one very common disconnect system, the drive shaft is splined at its opposite ends and is slidably coupled to the engine and accessory so that axial movement of the shaft will effect its disconnection from one of them. A nut member having a radially outwardly projecting stop portion thereon is threadedly mounted on an intermediate portion of the shaft and rotates therewith under normal operating conditions. To cause the disconnecting axial motion of the shaft, a pin or other rigid element is moved into the path of the rotating stop member. The stop member slams into the pin and instantaneously stops the rotation of the nut member. The shaft, still rotationally driven by the engine, axially advances itself relative to the stationary nut member to cause uncoupling of the engine and accessory.
Especially at high shaft speeds, this impact places a great deal of stress on the pin and can easily shatter it or bend it, thereby causing the disconnect mechanism to fail, in turn potentially damaging the accessory, the engine or both if a malfunction of either necessitated their disconnection in the first place. Moreover, it is important to note that the circumferential "window" presented by the rotating stop surface for receiving the pin is often guite limited, the stop portion itself very rapidly sequentially blocking and unblocking the movement of the pin trying to engage and stop it. The higher the shaft speed, the more difficult it is for the pin to properly engage the stop. As in the case of shattering or bending the pin, this problem can also cause the disconnect system to fail, or at least substantially increase the time required for disconnection to occur.
Other previously used disconnect systems have approached these stress and reliability problems by connecting separate portions of the drive shaft with a linking member purposely designed to be broken (by other components of the disconnect mechanism) when disconnection is desired. This, of course, negates the possibility of reusing or resetting the mechanism. It is good only for one use. Additionally, there is always the concern that the drive shaft's weak link will unexpectedly break of its own accord, leaving the engine-accessory system inoperative until the one-use disconnect system is rebuilt. In a great many applications, this situation is simply unacceptable.
It can be seen that there is a need for a high speed engine-accessory disconnect system which is reusable, highly reliable, operates with minimal stress on its components, and is easily and quickly resettable. Accordingly, it is an object of the present invention to provide such a system and to thereby eliminate or minimize above-mentioned and other problems and disadvantages associated with previous disconnect systems.